Manufacture of lenses for spectacles or eyeglasses.



H.- ORFORD. I MANUFACTURE OF LENSES FOR SPEGTAOLES 0R EYEGLASSES.

APPLIUATION FILED IIAN.30.1909.

' 943,449. I Patented Dec.14.1909.

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HENRY ORFORD, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR OF ONE-HALF TO SAMUEL J. TAYLOR, OFPHILADELPHIA, PENNSYLVANIA.

MANUFACTURE OF LENSES FOR SPEOTACLES 0R EYEGLASSES.

IatentedDec. 14, 1909.

Application filed January 30, 1909. Serial No. 475,111.

To all imam it may concern:

Be it known that I, ,HENRY'ORFORD, of Philadelphia in the couhty of Philadelphia and State of Pennsylvania, have invented certain new and usefu Improvements in the Manufacture of Lenses for Spectacles or Eyeglasses, whereof the followin is a specification, referencebeing had to tie accompanying drawings.

It is the object of my invention to produce what may be called a multi-foeal lens, that is to say, ,a lens the focal length .of which varies gradually as the line of vision passes th ough the upper or the lower part thereof. Heretofore bi-focal lenses have been produced-in whiclrdiflerent portions of the lenses have been ground to difierent curvature, but with a sharp line of demarcation between the two, which obscures the vision. My imention diflers from such lenses in that the variation of curvature is continuous from the top to the bottom of the lens, so that as the line of visionis lowered, the power of the lens gradually in creases. This I aecomplishby grinding the convex surface of the lens spherically, while the concave surface is given a parabolic curvature. The same principle may be ap plied to cylindrical lenses, and although I will describe my invention as applicable to spherically ground glasses, it is to be understood that the same principle applies to cyl- 'inders.

In the accompanying drawings, Figure I represents in vertical section a concavoconvex disk, from which I make my lens. Fig. II shows in similar section the dies employed for shaping this disk, so as to impart a parabolic curvature to its concave surface. Fig. III is a plan view of the disk when thus shaped, showing the portions ahereof used in the manufacture from it of two corresponding eye glass lenses. Fig. IV is a horizontal central section through a lens embodying my invention. Fig. V is a vertical central section through a lens enibodying my invention.

It will be understood that therurvatu-rcs and proportions of the drawings are magnitied in order to render visible to the eye curvatures which in practice may be very slight. l'n'the nmnufacture ofmy lens, I first produce by the ordinary method of grinding a concal vo-convex disk as illustrated in. Fig. I, the convex surface 1, being ground to the proper spherical curvature and the concave surface 2, being similarly ground to a spherical curvature. My in- ,vention as above stated depends upon the imparting to this concave surface of a parabolic curvature. But in practice it is exceedingly difficult, if not impossible, to grind such a curve. I therefore, resort to the following means :I prepare two metallic dies 4, and 5, (Fig. II), one of which, i, is provided with a spherical surface corresponding substantially with the convex surface 1, of the disk, while the other die, 5, is provided with v a convex parabolic surface 6, differing from the spherical concave surface of the lens. After the disk shown 1n Fig. I, has

been properly ground, it is heated 'to the point where its surfaces have become slightly plastic and capable of receiving under pres sure the impression of a mold, without, how-' ever, flowing to such an extent as to create bubbles or flaws in the glass. While in this plastic condition, it is placed between the dies and sufiicient pressure exerted to cause the disk to assume the curvatures illustrated in Fig. II. The parabolic surface6, imparts to the concave surface of the disk a corresponding curvature so that the focal length of the disk is greatest at the center and diminishes gradually as the line of vision approaches the edge. To produce from the disk thus obtained the required spectacle lens there are cut from it two lenses as illustrated in Fig. III, where 7 ,7 represent the two eye glass lenses in their relation to the entire disk. The dotted lines ,8, 8, in Fig. II, also represent the edges along which the cutting or grinding occurs in the production of the lens. The finished lens thus produced and which in cross section is illustrated by the section between the lines 8, 8, in Fig. II, is possessed of spherical curvature upon one sideand parabolic curvature upon the other side, which imparts to the lens a varying focal length as the line of vision'passes from the thinner edge at the top to the thicker edge at the bottom. By employing lenses of this character in spectacles or eyeglasses, all the advantages of the so-called bifocal lenses are secured with important additional advantages. In looking at objects far away, the eye usually employs the upper portion of the lens of an eye glaQs, and for this a long focal length is provided. In reading, the eye usually drops and employs the lower portion of the lens, and for this a smaller focal length is provided, but instead of a sharp line of demarcation between the two, the variation in curvature is gradually and wholly imperceptible to the eye, rendering the lens more serviceable and less noticeable upon the wearer.

I do not limit myself'to the recise construction of lens which I have 'escribed as variations therefrom will suggest themselves to those skilled in this art. The curves which I have described may vary, and also the method of imparting them to the lens, and as explained, the principle of co nstr 1ction which I have described is applicable equally to cylindrical as to spherical l'e'rises'.

Having thus described any invention, I

. 2. A lens for spectacles or eyeglasses, pro-.

vided with a convex surface having a spher- 1cal curvature, and a concave surface having a parabolic curvature, the two surfaces beedge to the other.

3. A spectacle lens provided with a convex ground surface having a spherical curvature, and a concave molded surface having a parabolic curvature, the latter surface being so related to, the former as to cause a gradual variation of the focal length of the lens as the line of vision passes from the upper ,edge to the lower edge.

In testimony whereof, I have hereunto signed. my name, at Philadelphia. Pennsyi- Vania, this twenty-seventh. day of January 1.909. -HENRY ORE-ORE.

Witnesses:

JAMES H. BELL, E. L. FULLERTON. 

